1. Field of the Invention
This invention generally relates to a numerical control apparatus, and more specifically to an apparatus having a teaching function and a method of teaching a machining program.
2. Description of the Related Art
Machining programs are specially designed for use in a numerical control (NC) apparatus. Machining programs are also known as "NC programs", and are composed of blocks of NC programming codes. These machining programs are input to an NC apparatus through input devices such as a paper tape reader or a flexible disk drive unit, and are used in the machining process of a workpiece.
The preparation of such machining programs is difficult because a special knowledge is needed of the materials of the workpiece, the conditions of the machining process, and the programming codes of various machine tools and the like.
The codes of the normal machining program generally are not defined if a workpiece has a free curved surface, because such codes typically define linear interpolation and circular interpolation. In such a case an NC apparatus having a teaching function is used. This type of NC apparatus is generally controlled by a machine tool operator in a factory.
The operator produces a machining program during manual operation mode of the NC apparatus by using a teaching mode within the NC apparatus. The resulting machining program is then used for machining of the next workpieces in a play back mode.
However, when using such an NC apparatus, the operator must operate the machine to produce all blocks of the machining program, resulting in an increase in the operator's work load. This increase may be significant since much more time is needed to produce such a machining program.
If an NC apparatus which does not have a teaching function is used, the operator must wait for the machining program to be changed by a programmer if any changes are required, so that response time becomes much longer. The programmer, in general, does not have information regarding machining conditions or the know-how which is required for machining at the machining spot, such as, for example, which tools are used in the machining process, the material of the workpiece, and the true shape of the workpiece.
Further, if a workpiece has a free curved surface, the programmer does not prepare the program to define the code of the machining program and the machining conditions described above in order to produce that surface. Thus the operator must operate in a manual mode or a manual data input mode (MDI mode) and set such machining conditions into the machine. When the workpiece is machined, the operator must operate in the manual operation mode or manual data input mode to produce such free curved surfaces. It is notably difficult to produce a free curved surface using manual operation and manual data input mode. As a result, if there exists a number of workpieces, the operator must repeat this difficult operation for each workpiece.
Since a typical NC apparatus having a teaching mode provides the teaching function only in the manual mode, there is no relationship between the normal automatic mode, the manual data input mode, or the manual mode.